The U.S. representative in the six-party talks on North Korea's nuclear weapons says the negotiations are having a positive effect. Negotiator Christopher Hill is rejecting critics' arguments that the talks have failed because North Korea is not accepting steps to verify that it is disabling its nuclear facilities.

Christopher Hill, the Assistant Secretary of State for East Asian and Pacific Affairs, says that in the three years the talks have been in progress, North Korea has not developed any further nuclear weapons.

"Since the September '05 agreement, they have not produced one gram of plutonium," he said. "And I think the six-party process can take some credit for that."

The six parties involved in the talks are North Korea, South Korea, Japan, China, Russia and the United States. At a meeting of the Asia Society, Tuesday, Hill said nobody has proposed a better alternative to the six-party talks.

"If you did not have a six-party process, what would you have? And I would argue to you, if we did not have a process and had nothing, we would have a lot more plutonium to deal with," he said.

The talks in Beijing broke down last week, after North Korea rejected a verification plan the other five countries had accepted, under which Pyongyang would put in writing the verbal commitments it has made on nuclear disarmament.

Hill says there more progress can still be made in the talks, even though the Bush administration leaves office five weeks from now.

"This issue of the verification protocol that we are dealing with is to do a couple of things," he said. "One, it is to verify what they have put in their declaration. That is, if it is 30 kilos [of plutonium], we need to verify that it is 30 and not 40 and not 50. We also need to verify the absence of any uranium enrichment program."

After three years of negotiating with North Korea, Hill admits that "it has been tough to build up a level of trust." But he hopes to convince officials in Pyongyang that the benefits of giving up their nuclear ambitions far outweigh what they could gain by continuing to develop the weapons.

"And maybe at that point North Korea will come to the understanding that most countries in the world have come to understand, which is that you do not need nuclear weapons to protect yourselves; you need good relations with your neighbors to protect yourself," he said.

Hill says he has not talked with anyone about whether he would remain in his post after President-elect Barack Obama takes office on January 20.